JP2010092698A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery suppressing an increase in internal resistance of the battery after high temperature storage, and an increase in internal resistance of the battery when the battery after high temperature storage is used at low temperature. <P>SOLUTION: The nonaqueous electrolyte secondary battery 1 includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative active material, and a nonaqueous electrolyte. The nonaqueous electrolyte contains 2.0 or less mass% of cyclic unsaturated sultone compound and 2.0 or less mass% of at least one cyclic sulfite ester selected from the group consisting of ethylene sulfite, 1,2-propylene glycol sulfite and vinyl ethylene sulfite to the total mass of the nonaqueous electrolyte. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

Nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries have high voltage and high energy density, and are therefore widely used, for example, as mobile phones and notebook personal computer power supplies.
In such a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as “battery”), a carbon material is generally used as the negative electrode active material, and a lithium transition metal composite oxide is used as the positive electrode active material, and ethylene is used as the non-aqueous electrolyte. A nonaqueous electrolytic solution in which a supporting salt such as LiPF ₆ is dissolved in a solvent such as carbonate (EC) or propylene pyrene carbonate (PC) is used.

Non-aqueous electrolyte secondary batteries are required to have excellent high-temperature storage performance. For example, a battery used for a mobile phone or the like that is left in a car parked outdoors in midsummer may be exposed to a high temperature environment.
If the nonaqueous electrolyte secondary battery is stored in a charged state in a high temperature environment, there is a problem that the electrolytic solution is oxidized or reductively decomposed on the positive and negative electrodes to grow a film, resulting in an increase in internal resistance.
As a means for solving such a problem of battery performance degradation after high-temperature storage, for example, a non-aqueous electrolyte secondary battery in which unsaturated sultone is added to a non-aqueous electrolyte is known (see Patent Document 1).
Patent Document 2 discloses a technique for improving high-temperature storage characteristics of a non-aqueous electrolyte secondary battery by containing ethylene sulfite in the non-aqueous electrolyte. Patent Document 3 discloses a vinylene carbonate compound in the non-aqueous electrolyte. And a vinyl ethylene sulfite compound, a composite film is formed on the negative electrode surface, and gas generation during continuous charging is suppressed, and a technique for improving discharge characteristics after continuous charging is disclosed. Yes.
JP 2002-329528 A JP 2002-170575 A JP 2005-166553 A

When the non-aqueous electrolyte described in Patent Document 1 is used, an increase in the internal resistance of the battery after high-temperature storage can be suppressed as compared with a battery using a non-aqueous electrolyte to which no unsaturated sultone is added. It was not a thing.
Moreover, when the non-aqueous electrolyte secondary battery described in Patent Document 2 or Patent Document 3 is used, the discharge characteristics during high-temperature storage are improved as compared with a battery using a non-aqueous electrolyte to which ethylene sulfite is not added. An increase in the internal resistance of the battery after high temperature storage could not be suppressed.
Further, in recent years, non-aqueous electrolyte secondary batteries have been increasingly demanded as power sources for moving bodies such as electric vehicles and hybrid cars. Battery performance is required. For example, it may be used in a low temperature environment after being exposed to a high temperature environment in an area where the temperature difference of the day is large. There is a problem that the internal resistance of the battery further increases and the output decreases in a low temperature environment than in a normal temperature environment.

  The present invention has been completed on the basis of the above circumstances, suppresses an increase in the internal resistance of the battery after high-temperature storage, and reduces the internal resistance of the battery when the battery after high-temperature storage is used at a low temperature. It aims at providing the nonaqueous electrolyte secondary battery which suppresses an increase.

  As a result of intensive studies to solve the above problems, the present inventors have added a predetermined amount of a cyclic unsaturated sultone compound and a predetermined amount of a cyclic sulfite ester to the nonaqueous electrolyte, thereby independently using them. The increase in the internal resistance of the battery after high temperature storage can be suppressed more significantly than the added one, and the increase in the internal resistance of the battery when using the battery after high temperature storage at a low temperature can be suppressed. I found it.

That is, the present invention provides a nonaqueous electrolyte secondary battery comprising a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a nonaqueous electrolyte, wherein the nonaqueous electrolyte is a total of the nonaqueous electrolyte. The cyclic unsaturated sultone compound represented by the following general formula (1) is contained in an amount of 2.0% by mass or less based on the mass, and is composed of ethylene sulfite, 1,2-propylene glycol sulfite, and vinyl ethylene sulfite. A nonaqueous electrolyte secondary battery comprising 2.0% by mass or less of one or more cyclic sulfites selected from the group.
In addition, the content of the cyclic unsaturated sultone compound represented by the general formula (1) is preferably 0.1% by mass or more with respect to the total mass of the nonaqueous electrolyte, and the content of the cyclic sulfite is the total amount of the nonaqueous electrolyte. 0.1 mass% or more is preferable with respect to mass.

(In the formula, R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, fluorine or a hydrocarbon group having 1 to 4 carbon atoms which may contain fluorine, and n is an integer of 1 to 3). is there).

  By adding a predetermined amount of a cyclic unsaturated sultone compound and a predetermined amount of a cyclic sulfite to the non-aqueous electrolyte, the internal resistance of the battery after storage at a high temperature is remarkably increased as compared with the case where these are added alone. Although the details of the reason why it is possible to suppress the increase in the internal resistance of the battery when it is suppressed and the battery after high temperature storage is used at a low temperature are not clear, it is presumed as follows.

A hybrid coating composed of a cyclic unsaturated sultone compound added to the electrolyte and a cyclic sulfite is formed on the electrode plate surfaces of the positive electrode and the negative electrode, and the hybrid coating suppresses the decomposition reaction of the electrolyte and is stored at a high temperature. It is thought that the increase in the internal resistance of the battery after the high temperature storage was suppressed while the increase in the internal resistance of the battery after the high temperature storage was suppressed.
In the present invention, the cyclic unsaturated sultone compound is preferably 1,3-propene sultone. This is because it is low in self-degradability and easy to handle.

  According to the present invention, there is provided a nonaqueous electrolyte secondary battery that suppresses an increase in internal resistance of a battery after storage at high temperature and suppresses an increase in internal resistance of the battery when the battery after high temperature storage is used at a low temperature. can do.

<Embodiment 1>
Embodiment 1 of the present invention will be described with reference to FIG.
FIG. 1 is a schematic cross-sectional view of a prismatic nonaqueous electrolyte secondary battery 1 according to an embodiment of the present invention. This non-aqueous electrolyte secondary battery 1 (hereinafter also simply referred to as “battery”) includes a positive electrode plate 3 formed by applying a positive electrode mixture to a positive electrode current collector made of aluminum foil, and a negative electrode current collector made of copper foil. A power generation element 2 in which a negative electrode plate 4 formed by applying a negative electrode mixture to a battery and a non-aqueous electrolyte wound in a spiral shape with a separator 5 interposed therebetween are housed in a battery case 6.

  A battery lid 7 provided with a safety valve 8 is attached to the battery case 6 by laser welding, the negative electrode plate 4 is connected to a negative electrode terminal 9 at the upper part of the battery case 6 via a negative electrode lead 11, and the positive electrode plate 3 is a positive electrode. The battery lid 7 is connected via the lead 10.

  The positive electrode plate 3 includes a positive electrode mixture layer containing a positive electrode active material capable of occluding and releasing lithium ions on both surfaces of a positive electrode current collector formed of a metal such as aluminum. A positive electrode lead 10 is welded to a portion of the positive electrode current collector where the positive electrode mixture layer is not formed.

There is no restriction | limiting in particular as a positive electrode active material of the nonaqueous electrolyte secondary battery used in this invention, A various material can be used suitably. For example, a composite oxide represented by the general formula Li _x M1O _2-δ (where M1 represents Co, Ni, or Mn, 0.4 ≦ x ≦ 1.2, 0 ≦ δ ≦ 0.5), or A compound containing at least one element selected from Al, Mn, Fe, Ni, Co, Cr, Ti, Zn, P, and B can be used for these composite oxides.
Moreover, the general formula _{Li x Ni p M2 q M3 r} O 2-δ ( However, M2, M3 are respectively Al, Mn, Fe, Ni, Co, Cr, Ti, Zn, at least one element selected P, from B 0.4 ≦ x ≦ 1.2, 0.8 ≦ p + q + r ≦ 1.2, and 0 ≦ δ ≦ 0.5) can be used.
Moreover, the general formula _Li x _M4 s PO ₄ (provided that, M4 are 3d transition metal, 0 ≦ x ≦ 2,0.8 ≦ s ≦ 1.2) can be a compound having an olivine structure represented by, Further, this compound may be used by coating with amorphous carbon.

  A conductive agent, a binder, or the like can be added to the positive electrode active material. As the conductive agent, an inorganic compound or an organic compound can be used. As the inorganic compound, acetylene black, carbon black, graphite or the like can be used, and as the organic compound, for example, a conductive polymer such as polyaniline can be used. As the binder, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyacrylonitrile, or the like can be used alone or in combination.

  Next, the negative electrode plate 4 will be described. The negative electrode plate 4 includes a negative electrode mixture layer containing a negative electrode active material capable of occluding and releasing lithium ions on both surfaces of a negative electrode current collector formed of a metal such as copper. A negative electrode lead 11 is welded by ultrasonic welding to a portion of the negative electrode current collector where the negative electrode mixture layer is not formed.

As the negative electrode active material contained in the negative electrode mixture layer, carbonaceous materials such as graphite, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), Al, Si, Pb, Sn, Zn , an alloy compound of Cd or the like and the lithium metal Li, the general formula M5O _z (except M5 is, W, Mo, Si, Cu, and at least one element selected from Sn, 0 ≦ z ≦ 2) is represented by Metal oxides or mixtures thereof can be used. Similarly to the positive electrode active material, a binder such as polyvinylidene fluoride can be added to the negative electrode active material.

  As the separator 5, a woven fabric, a non-woven fabric, a synthetic resin microporous film, or the like can be used. In particular, a synthetic resin microporous film can be suitably used. Among them, it is possible to use a heat-resistant resin obtained by processing polyethylene and polypropylene microporous membranes, aramids, or the like, or a polyolefin microporous membrane such as a microporous membrane obtained by combining these.

The non-aqueous electrolyte is prepared by dissolving an electrolyte salt or the like in a non-aqueous solvent.
Examples of the electrolyte salt include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ CO ₂ , LiCF ₃ (CF ₃ ) ₃ , LiCF ₃ (C ₂ F ₅ ) ₃ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO. _{3, LiCF 3 CF 2 CF 2} SO 3, LiN (SO 2 CF 3) 2, LiN (SO 2 CF 2 CF 3) 2, LiN (COCF 3) 2, LiN (COCF 2 CF 3) 2, LiPF 3 ( CF ₂ CF ₃ ) ₃ , LiB (C ₂ O ₄ ) ₂ , LiBF ₂ C ₂ O ₄ , LiP (C ₂ O ₄ ) ₃ , LiPF ₂ (C ₂ O ₄ ) ₂ , LiPF ₄ C ₂ O _4, etc. It can be used alone or in combination of two or more. It is preferable to use LiPF ₆ as the electrolyte salt, or to mix and use a small amount of the electrolyte salt mainly composed of LiPF ₆ .

Nonaqueous solvents for dissolving the electrolyte salts include cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and chain carboxylates such as methyl acetate and ethyl acetate. , Γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, phosphazenes and the like can be used alone or in admixture of two or more.
Further, in order to improve battery characteristics, a small amount of compound may be mixed in the non-aqueous electrolyte, carbonates such as vinylene carbonate and methyl vinylene carbonate, vinyl esters such as vinyl acetate and vinyl propionate, diallyl sulfide, Sulfides such as allyl phenyl sulfide, sulfones such as bis (vinylsulfonyl) methane and butadiene sulfone, chain sulfonates such as methyl methanesulfonate and ethyl methanesulfonate, sulfate esters such as dimethyl sulfate and diethyl sulfate Aromatic compounds such as benzene and toluene, halogen-substituted alkanes such as perfluorooctane, tristrimethylsilyl borate, bistrimethylsilyl sulfate, tristrimethylsilyl phosphate, and tetrakistrimethylsilyl titanate. Glycol ester and the like can be used alone or in admixture of two or more.

  In the present invention, the nonaqueous electrolyte includes a group consisting of a cyclic unsaturated sultone compound represented by the following general formula (1), ethylene sulfite, 1,2-propylene glycol sulfite, and vinyl ethylene sulfite. And one or more cyclic sulfites selected from the above.

(In the formula, R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, fluorine or a hydrocarbon group having 1 to 4 carbon atoms which may contain fluorine, and n is an integer of 1 to 3). is there).

  Examples of the cyclic unsaturated sultone compound include 1,3-propene sultone, 1-methyl-1,3-propene sultone, 1-fluoro-1,3-propene sultone, 1,1-dimethyl-1,3-propene. Sultone, 1,2-dimethyl-1,3-propene sultone, 2-methyl-1,3-propene sultone, 2-fluoro-1,3-propene sultone, 3-methyl-1,3-propene sultone, 3- Fluoro-1,3-propene sultone, 1,4-butene sultone, 1-methyl-1,4-butene sultone, 1-fluoro-1,4-butene sultone, 2-methyl-1,4-butene sultone, 2-fluoro-1 , 4-butene sultone, 3-methyl-1,4-butene sultone, 3-fluoro-1,4-butene sultone, 4-methyl-1,4-butene sultone Emissions, 4-fluoro-1,4-butene sultone, and the like. Of these, 1,3-propene sultone represented by the following formula (2) is preferable because it has low self-degradability and is easy to handle.

In the present invention, a hydrocarbon group having 5 to 5 carbon atoms or a cyclic unsaturated sultone having 4 or more in n is not preferable because R1 to R4 cause a decrease in liquid injection property due to an increase in viscosity of the nonaqueous electrolyte.

In the present invention, the non-aqueous electrolyte contains 2.0% by mass or less of a cyclic unsaturated sultone compound based on the total mass of the non-aqueous electrolyte, ethylene sulfite, 1,2-propylene glycol sulfite, and One or more cyclic sulfites selected from the group consisting of vinylethylene sulfite are contained in an amount of 2.0% by mass or less.
When the amount of the cyclic unsaturated sultone compound exceeds 2.0% by mass with respect to the total mass of the nonaqueous electrolyte, gas is generated due to the decomposition reaction and the internal resistance increases. On the other hand, if the amount of cyclic sulfite exceeds 2.0% by mass with respect to the total mass of the nonaqueous electrolyte, gas is generated by the decomposition reaction and the internal resistance increases.
When the amount of the cyclic unsaturated sultone compound and the cyclic sulfite is less than 0.1% by mass with respect to the total mass of the nonaqueous electrolyte, the effect of suppressing the increase in the internal resistance of the battery is small. Therefore, the content of the cyclic unsaturated sultone compound is preferably 0.1% by mass or more based on the total mass of the nonaqueous electrolyte, and the content of the cyclic sulfite ester is based on the total mass of the nonaqueous electrolyte. 0.1 mass% or more is preferable.

  That is, in the battery of the present invention, by using a non-aqueous electrolyte containing the above-mentioned amount of the cyclic unsaturated sultone compound and the above-mentioned amount of the cyclic sulfite ester, the battery is more marked than a battery using a non-aqueous electrolyte containing these alone. The increase in the internal resistance of the battery after high temperature storage can be suppressed, and the increase in the internal resistance of the battery when the battery after high temperature storage is used at a low temperature can be suppressed.

In a battery having a non-aqueous electrolyte containing a cyclic unsaturated sultone compound and a cyclic sulfite ester, the mechanism for suppressing the increase in internal resistance after high-temperature storage is not clear, but is presumed as follows.
A hybrid coating composed of a cyclic unsaturated sultone compound added to the electrolyte and a cyclic sulfite is formed on the electrode plate surfaces of the positive electrode and the negative electrode, and the hybrid coating suppresses the decomposition reaction of the electrolyte and is stored at a high temperature. It is considered that the increase in the internal resistance of the battery after the high temperature storage is suppressed while the increase in the internal resistance of the battery after the high temperature is suppressed.

<Example>
Hereinafter, although the Example and comparative example of this invention are shown, this invention is not limited to this.
1. Production of Battery of Example 1 A nonaqueous electrolyte secondary battery having the form shown in FIG. 1 was produced by the following method.
(1) Production of positive electrode plate 5 parts by mass of polyvinylidene fluoride as a binder, 5 parts by mass of acetylene black as a conductive agent, and 90 masses of LiNi _0.17 Co _0.66 Mn _0.17 O ₂ as a positive electrode active material After adding N-methyl-2-pyrrolidone to the mixture and preparing a paste, this was applied to both sides of a positive electrode current collector made of aluminum foil with a thickness of 20 μm and dried. A positive electrode plate 3 was prepared and a positive electrode lead 10 was provided.

(2) Preparation of negative electrode plate After adding 92 parts by mass of non-graphitizable carbon as a negative electrode active material and 8 parts by mass of polyvinylidene fluoride as a binder to N-methyl-2-pyrrolidone and preparing it in a paste form This was applied to both surfaces of a negative electrode current collector made of copper foil having a thickness of 10 μm and dried to prepare the negative electrode plate 4, and the negative electrode lead 11 was provided.

(3) Fabrication of battery A polyethylene microporous membrane was used as the separator.
As the non-aqueous electrolyte, a non-aqueous electrolyte prepared by the following method was used. In a mixed solvent of ethylene carbonate (EC): diethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 3: 3: 4 (volume ratio), LiPF ₆ was dissolved to 1 mol / L after preparation, 0.1% by mass of 1,3-propene sultone (PSL) and 0.1% by mass of vinyl ethylene sulfite (VES) are added to the total mass of the non-aqueous electrolyte to obtain a non-aqueous electrolyte. Prepared.
Using these materials, five cells of the nonaqueous electrolyte secondary battery of Example 1 having a capacity of 450 mAh were produced.

2. Production of batteries of Examples 2 to 28 and Comparative Examples 1 to 35 0.1% by mass of 1,3-propene sultone (PSL) and 0.1% by mass of vinylethylene with respect to the total mass of the nonaqueous electrolyte The nonaqueous electrolyte secondary of Examples 2 to 16 and Comparative Examples 1 to 15 were the same as Example 1 except that the amounts of PSL and VES shown in Table 1 were added instead of sulfite (VES). A battery was produced.

  Instead of 0.1% by mass of 1,3-propene sultone (PSL) and 0.1% by mass of vinyl ethylene sulfite (VES) with respect to the total mass of the nonaqueous electrolyte, the amounts shown in Table 2 were used. Nonaqueous electrolyte secondary batteries of Examples 17 to 20 and Comparative Examples 16 to 22 are the same as Example 1 except that 1,3-propene sultone (PSL) and ethylene sulfite (ES) are added. Was made.

Instead of 0.1% by mass of 1,3-propene sultone (PSL) and 0.1% by mass of vinyl ethylene sulfite (VES) with respect to the total mass of the nonaqueous electrolyte, the amounts shown in Table 3 were used. The nonaqueous electrolyte secondary batteries of Examples 21 to 24 and Comparative Examples 23 to 28 were the same as Example 1 except that 1,4-butene sultone (BSL) and vinyl ethylene sulfite (VES) were added. Was made.
Instead of 0.1% by mass of 1,3-propene sultone (PSL) and 0.1% by mass of vinyl ethylene sulfite (VES) with respect to the total mass of the nonaqueous electrolyte, the amounts shown in Table 4 were used. Examples 25-28 and Comparative Examples 29-35 are the same as Example 1 except that 1,3-propene sultone (PSL) and 1,2-propylene glycol sulfite (PGS) were added. A water electrolyte secondary battery was produced.

3. Evaluation Test (1) Battery Performance Test after High Temperature Storage (i) Initial Discharge Capacity Confirmation Test Using each battery of Examples 1-28 and Comparative Examples 1-35, an initial discharge capacity confirmation test was performed by the following method. .
By charging each battery to 4.2 V at a constant current of 450 mA at 25 ° C. and further charging for a total of 3 hours at a constant voltage of 4.2 V, and then discharging at a constant current of 450 mA and a final voltage of 2.5 V. The initial discharge capacity was measured.

(Ii) Storage test at 60 ° C. Each battery after the initial discharge capacity measurement was subjected to a storage test at 60 ° C. by the following method. Charge to 4.03 V at a constant current of 450 mA, further charge for a total of 3 hours at a constant voltage of 4.03 V, set the SOC of the battery to 80%, and store in a constant temperature bath at 60 ° C. for 30 days (1 month) did. After cooling to 25 ° C., each battery was discharged at a constant current of 450 mA and a final voltage of 2.5 V, and then charged and discharged under the same conditions as in the initial discharge capacity confirmation test. This storage test at 60 ° C. was repeated for 6 months.
Here, “SOC is set to 80%” represents that the amount of charged electricity is 80% with respect to the capacity of the battery.

(Iii) DC resistance value at 25 ° C. The batteries of Examples 1 to 5, the batteries of Examples 7 to 10, the batteries of Examples 12 to 16, and the batteries of Comparative Examples 1 to 15 after the storage test at 60 ° C. Each battery was charged to 3.73 V at a constant current of 450 mA, and further charged for a total of 3 hours at a constant voltage of 3.73 V, so that the SOC of the battery was set to 50%. After holding at 25 ° C. for 5 hours, 90 mA (I1 ), The voltage (E1) when discharged for 10 seconds and the voltage (E2) when discharged for 10 seconds at 225 mA (I2) were measured.
Here, “SOC to 50%” indicates that the amount of charged electricity is 50% with respect to the capacity of the battery.

Using the measured values, the DC resistance value (Rx) at 25 ° C. was calculated by the following formula and shown in Table 1.
Rx = (E1-E2) / Discharge current (I2-I1)
If the DC resistance value was 100 mΩ or less, it was judged that the increase in internal resistance after high-temperature storage could be suppressed.

(Iv) DC resistance value at −20 ° C. The batteries of Examples 1 to 28 and Comparative Examples 1 to 35 after the storage test at 60 ° C. are charged to 3.73 V at a constant current of 450 mA, and further set to 3.73 V constant. The battery SOC was set to 50% by charging the battery for a total of 3 hours, held at −20 ° C. for 5 hours, and then discharged at 90 mA (I1) for 10 seconds (E3) and 225 mA (I2). The voltage (E4) when discharged for 10 seconds was measured.
Here, “SOC to 50%” indicates that the amount of charged electricity is 50% with respect to the capacity of the battery.

Using the above measured values, DC resistance values (Ry) at −20 ° C. were calculated by the following formulas and shown in Tables 1 to 4. If the DC resistance value was 500 mΩ or less, it was judged that the increase in internal resistance due to low temperature use could be suppressed.
Ry = (E3-E4) / Discharge current (I2-I1)

  In Tables 1 to 4, the amount of the cyclic unsaturated sultone compound added to the non-aqueous electrolyte (mass% based on the total mass of the non-aqueous electrolyte) and the amount of the cyclic sulfite ester (mass based on the total mass of the non-aqueous electrolyte). %). In the table, the resistance value means a DC resistance value.

4). Results and Discussion (1) A book comprising a non-aqueous electrolyte containing 2.0% by mass or less of a cyclic unsaturated sultone compound and 2.0% by mass or less of a cyclic sulfite ester relative to the total mass of the non-aqueous electrolyte. In the batteries of the invention (Examples 1 to 5, Examples 7 to 10, and Examples 12 to 16), the DC resistance value at 25 ° C. was 100 mΩ or less, and an increase in internal resistance after high-temperature storage could be suppressed.

  However, in batteries (Comparative Examples 1 to 15) in which at least one of the cyclic unsaturated sultone compound and the cyclic sulfite is out of the above content range, the DC resistance value is high, and the internal resistance after high-temperature storage is increased. Could not be suppressed.

Specifically, in the battery (Comparative Example 1, Comparative Example 6, Comparative Example 8 to 10) in which only 0.1% by mass to 2.0% by mass of the cyclic unsaturated sultone compound is added, the cyclic unsaturated sultone compound and the cyclic compound are cyclic. The resistance value was only slightly smaller than that of the battery in which neither sulfite was added (Comparative Example 1). Moreover, in the battery (Comparative Examples 2 to 4) in which only 0.1% by mass to 2.0% by mass of the cyclic sulfite ester is added, the battery in which neither the cyclic unsaturated sultone compound nor the cyclic sulfite ester is added (Comparative Example 1). The resistance value was only slightly smaller than that.
In the battery (Comparative Examples 12 to 15) to which 4.0% by mass of the cyclic unsaturated sultone compound was added and the battery (Comparative Examples 5, 7 and 11) to which 5.0% by mass of the cyclic sulfite was added, the cyclic unsaturated sultone compound and The resistance value was larger than that of the battery to which neither cyclic sulfite was added (Comparative Example 1). This is considered to be that when either a cyclic unsaturated sultone compound or a cyclic sulfite is contained in a predetermined amount or more, gas generation occurs due to decomposition of the electrolytic solution and internal resistance increases.

(2) Internal resistance in low temperature use Non-aqueous electrolysis containing 2.0% by mass or less of cyclic unsaturated sultone compound and 2.0% by mass or less of cyclic sulfite with respect to the total mass of the non-aqueous electrolyte. In the battery of the present invention (Examples 1 to 28) provided with the liquid, the direct current resistance value at −20 ° C. was 500 mΩ or less, and the increase in internal resistance when the battery after high-temperature storage was used at low temperature could be suppressed. .
In addition, among the batteries of the present invention, those containing 0.2 to 1.0% by mass of PSL and 0.3 to 1.0% by mass of VES (Examples 6 to 9, Examples 11 to 13) In addition, particularly preferable results were obtained with 0.2% to 1.0% by mass of BSL and 0.5% by mass of VES (Examples 22 to 23).
However, in the batteries (Comparative Examples 1 to 15) in which at least one of the cyclic unsaturated sultone compound and the cyclic sulfite is out of the above content range, the DC resistance value is high, and the internal resistance in low temperature use after high temperature storage. The increase in the amount could not be suppressed.

  Specifically, in the battery (Comparative Example 1, Comparative Example 6, Comparative Example 8-10, Comparative Example 23, Comparative Example 25) in which only 0.1% by mass to 2.0% by mass of the cyclic unsaturated sultone compound was added. The resistance value was only slightly smaller as compared with the battery in which neither the cyclic unsaturated sultone compound nor the cyclic sulfite was added (Comparative Example 1). Moreover, in the battery (Comparative Examples 2-4, Comparative Examples 16-18) which added only 0.1 mass%-2.0 mass% of cyclic sulfites, neither cyclic unsaturated sultone compound and cyclic sulfites were added. The resistance value was only slightly smaller than that of the battery (Comparative Example 1).

  Batteries added with 4.0% by mass of cyclic unsaturated sultone compound (Comparative Examples 12-15, Comparative Examples 20-22, Comparative Example 27, Comparative Example 28), and batteries added with 5.0% by mass of cyclic sulfite ester Among the batteries except Comparative Example 24 (Comparative Example 5, Comparative Example 7, Comparative Example 11, Comparative Example 18-19, Comparative Example 24, and Comparative Example 26), both the cyclic unsaturated sultone compound and the cyclic sulfite were not added. The resistance value was larger than that of the battery (Comparative Example 1). This is considered to be that when either a cyclic unsaturated sultone compound or a cyclic sulfite is contained in a predetermined amount or more, gas generation occurs due to decomposition of the electrolytic solution and internal resistance increases.

  <Other embodiments>

  The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) Although the rectangular battery is shown in the above embodiment, the shape of the battery may be, for example, a cylindrical shape.

(2) In the above examples, LiNi _0.17 Co _0.66 Mn _0.17 O ₂ was used as the positive electrode active material, but LiNi _1/3 Co _1/3 Mn _1/3 O ₂ was used as the positive electrode active material. LiCoO ₂ , LiNiO ₂ , LiNi _1/2 Mn _1/2 O _2, or the like may be used.

  (3) In the above examples, non-graphitizable carbon is used as the negative electrode active material, but carbon black, graphite, graphitizable carbon (soft carbon), or the like may be used as the negative electrode active material.

Sectional drawing of the battery of Embodiment 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Nonaqueous electrolyte secondary battery 3 ... Positive electrode plate 4 ... Negative electrode plate 5 ... Separator 6 ... Battery case

Claims (2)

A non-aqueous electrolyte secondary battery comprising a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a non-aqueous electrolyte,
The nonaqueous electrolyte contains 2.0% by mass or less of a cyclic unsaturated sultone compound represented by the following general formula (1) with respect to the total mass of the nonaqueous electrolyte.
A non-aqueous electrolyte secondary battery comprising 2.0% by mass or less of one or more cyclic sulfites selected from the group consisting of ethylene sulfite, 1,2-propylene glycol sulfite, and vinyl ethylene sulfite.

(In the formula, R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, fluorine or a hydrocarbon group having 1 to 4 carbon atoms which may contain fluorine, and n is an integer of 1 to 3). is there). The non-aqueous electrolyte secondary battery according to claim 1, wherein the cyclic unsaturated sultone compound is 1,3-propene sultone.

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